1. Field of the Invention
The present invention relates to a pulse radar device having pulsed storage devices arranged in the signal analysis component, and is more particularly concerned with such an arrangement in which the storage devices comprise shift registers whose control pulse train is derived from a reference frequency, and wherein, within the radar period duration, two time zones are defined, an actual analysis zone in which signal processing is carried out with the pulse train frequency determined by the requisite range resolution, and a second time zone, a dead zone, in which a different pulse train frequency is selected.
2. Description of the Prior Art
The German Published Application No. 18 15 660, which corresponds to British Letters Patent No. 1,235,750 discloses a pulse radar device in which, in FIG. 2 thereof, the time between two transmitted pulses is divided into two time zones. In the first time zone, a counter is actuated which is started on the transmission of a transmitted pulse and which releases the timing pulses to the shift registers of the radar device for a specific length of time. At the end of the specific length of time, but before the transmission of the next transmitted pulse, the timing pulse feed is interrupted and, consequently, the mode of operation of the shift registers of the radar device is changed.
The German Published Application No. 25 40 584 is concerned with the problem which occurs when radar devices operate with a variable pulse frequency. The mode of operation of the shift registers required in the radar device for the digital signal processing in that system, for example, is such that the signal values in a first time zone of the receiving period are processed independently of the relevant pulse repetition frequency with the pulse train frequency provided for the shortest period duration at the maximum pulse repetition frequency. In the case of operation with a lower pulse repetition frequency, during the remainder of the time resulting from the extended period duration, the supply of input signals and/or the further processing of the echo signals is blocked.
The German Published Application No. 25 40 584 also poses another solution to the problem occurring in the event of a change in the pulse repetition frequency of the radar device, wherein, in the event of a transfer to a lower pulse repetition frequency, the pulse train frequency for the shift register is transferred in the same ratio so that the same number of register positions in the shift register is always used, whereas the pulse train frequency experiences a corresponding change. The pulse train frequency for the keying of the transmitter, for the transmitting-receiving transfer switch, and for the pulse trains for the shift registers is derived from a common pulse generator, and it is necessary to produce a number of shift pulse trains for controlling the registers which corresponds to the number of desired range channels within the period duration.
When shift registers are used which have a specific length which is normally greater than the special register length required for the processing of the signals, difficulties frequently occur. For example, the requirement can exist that 110 channels (range channels) are required for the range resolution, whereas 128 storage positions are available in the registers. From the German Published Application No. 25 40 584 it is known that the shift pulse trains for the production of the relevant range channels can consist of whole number multiples of the pulse frequency. Making the shift pulse train frequency a whole numbered multiple of the pulse repetition frequency has the advantage that, although spectral components occur as interferences, spectral components are suppressed by the blocking zones of the moving target filters as they correspond approximately in their spectral distribution to that of a so-called fixed target.
In the second time zone, i.e. in that zone within the receiving period which, with a lower pulse repetition frequency, occurs as residual time, it is possible to employ a heavily decelerated shift pulse train in accordance with the German Published Application No. 25 40 584. However, all the values must have passed through the entire shift register by the beginning of the next receiving period. As the first time zone, i.e. the actual receiving zone, is predetermined and the pulse repetition frequency and thus the period duration are also established, it is no longer possible to freely select the second time zone within the period duration. On the other hand, the remaining number of registers of the shift registers still available at the end of the receiving zone is likewise predetermined, so that the processing can meet with considerable difficulties as too many parameters are fixed. For example, in most cases with the known realization mentioned above, the shift pulse train frequency for the second time zone will not be able to be selected in a simple whole numbered ratio to the frequency of the first sub-zone. This results in the need for an increased expense in control devices (a special, additional pulse generator or the like) for the production of the pulse train frequency.